Pitch control mechanism for bladed rotor

ABSTRACT

Two Z-crank mechanisms connect at different stations to a rotor swashplate so that translation of the mechanisms causes collective pitch variation of the blades and so that rotation of the mechanisms either together or separately causes cyclic pitch variations of the blades and wherein the portions of the Z-crank mechanisms which connect directly to the rotor swashplate are positioned on opposite sides thereof to permit a minimum diameter installation.

United States Patent Arthur W. Linden Shelton, Conn.

Sept. 18, 1969 Apr. 13, 1971 United Aircraft Corporation East Hartford,Conn.

Inventor App]. No. Filed Patented Assignee PITCH CONTROL MECHANISM FORBLADED ROTOR Primary Examiner-Everette A. Powell, Jr.

Att0rneyVernon F. Hauschild ABSTRACT: Two Z-crank mechanisms connect atdifferent stations to a rotor swashplate so that translation of themechanisms causes collective pitch variation of the blades and so thatrotation of the mechanisms either together or separately causes cyclicpitch variations of the blades and wherein the portions of the Z-crankmechanisms which connect directly to the rotor swashplate are positionedon opposite sides thereof to permit a minimum diameter 11Claims,9Drawing Figs.

U.S.Cl 416/130, 416/115 Int. Cl B64c 27/74 FieldofSearch 416/127,

130, 148, 98, 112-416 installation.

10 X6 52 3 3 i? Fr Z8 54 1 15$ 46 52 I 1 "21a 4! Z L 1 1 v 6A 74 I 76 72PATENT ED APR 1 3 197i sum 3 0F 6 PATENTEU APR 1 3:971 3; 574483 RATENTED APR 1 3 m SHEET 6 BF 6 ENGINE 1 PITCH CONTROL MECHANISM FOR BLADEDROTOR CROSS-REFERENCE TO RELATED APPLICATIONS A related application wasfiled on even date in the name of Harold Ulisnik entitled Pitch controlMechanism For Bladed Rotor" and which includes generic claims to theconstructions taught herein and specific claims to the FIG. 9construction.

BACKGROUND OF THE INVENTION 1. Field of Invention This invention relatesto mechanism for varying the pitch of blades on a rotor and moreparticularly to varying the pitch both cyclically about any selectedaxis and collectively.

2. Description of the Prior Art In the rotor blade pitch change art, itis a unique requirement of the helicopter rotor that the blades becapable of pitch change both collectively and cyclically to effectproper aircraft control inpitch, roll and yaw. In the past this has beenaccomplished by supporting the rotor on a mast projecting from thefuselage and utilizing a swashplate external of the mast which isconnected to the blade pitch horns by connecting rods and which isactuatable by a plurality of hydraulic cylinder piston arrangements sothat swashplate translation effects collective pitch change of theblades and swashplate tilt effects cyclic pitch change of the blades.With this arrangement all of the pitch change mechanism is positionedexternal of the rotor mast thereby producing substantial drag. Inaddition in a coaxial rotor system control of the upper rotor isdifficult to achieve without excessive mechanical complexity, especiallywhen the upper rotor controlmust be independent from the lower rotorcontrol. This prior art construction is shown in U.S. Pat. No.3,199,601.

Wherever the term inner rotor" appears in the specification itidentifies that rotor which is closer to the fuselage, whereas the termouter rotor" identifies that rotor which is outboard or farther from thefuselage than the inner rotor".

Another approach in controlling helicopter-type aircraft was taught inthe Cierva Air Horse described fully in the Apr. 8, 1949 issue of TheAeroplane. In this construction, three helicopter lift rotors were used,two of them offset from the longitudinal centerline of the fuselage atthe forward end of the aircraft and one of them positioned along thelongitudinal centerline at the rear of the aircraft. In the Air Horse,aircraft pitch and roll are controlled by blade collective pitchvariation only. Cyclic pitch is used solely for yaw control and a singleZ- crank mechanism is utilized to produce cyclic pitch variation about asingle axis of the rotor to effect a yaw control. It would be impossiblewith this construction to obtain cyclic pitch variation about any otheraxis than the single selected axis.

Single Z-cranks have been used elsewhere, such as in U.S. Pat. Nos.1,750,778 and 2,333,366 to vary blade pitch. In these constructions,however, the single Z-crank is located in the blade of the helicopterand therefore adds to the rotor profile and serves to permit blade pitchvariation about a single axis only.

U.S. Pat. Nos. 2,097,117 and 2,097,118 use a single Z- crank arrangementto tilt the entire drive system of a rotor about a single axis. Such asystem requires powerful, heavy and complicated actuating mechanisms andis therefore not desirable.

Pullin U.S. Pat. No. 2,651,480 which bears a striking resemblance inconstruction to the aforementioned Cierva Air Horse, utilizes a singleZ-crank to effect cyclic pitch variation about a single axis as in theAir Horse; and, while he utilizes a second Z-crank, this second Z-crankis utilized solely to cause the first Z-crank to translate to eflectcollective pitch variation.

It will accordingly be seen that Z-crank mechanisms have not been usedin helicopter rotors to produce cyclic pitch variation about anyselected axis and to also produce collective pitch. In constructionswhich were capable of accomplishing these functions, such as thosedescribed above in connection with U.S. Pat. No. 3,199,601, pitchcontrol mechanism generally has had to be utilized external of the rotorhead, thereby adding to the frontal area and drag created by the rotorin operation.

In the past, the controlling of blade pitch on concentriccounterrotating rotors has presented a particularly troublesome problemwhich could not be met by the use of conventional external swashplatemechanisms. To solve this problem, double swashplates had to be usedwith the first swashplate positioned below the inner or lower rotor andcontrolling the inner rotor pitch and with the second swashplatepositioned between the two rotors and controlling the outer or upperrotor pitch, both swashplates and related mechanisms being external ofthe rotor drive shafts. While it is conventional to make a swashplate ofthe rotatable-stationary member construction, in this construction, itis necessary to make the swashplate for the outer rotor to include tworotatable members to account for counterrotation of the blades. This, ofcourse, is a highly complicated system, presents substantial frontalarea, large diameter and dragcreating mechanisms and also has thedisadvantage that identical pitch change variations have to be made toboth rotors and therefore the rotors could not be controlledindependently.

Attempts have been made to effect independent control of two concentricrotors by passing the control servos for the outer rotor through theouter rotor drive shaft to the swashplate which was positioned withinthe outer rotor drive shaft, however, this proved unsuccessful becauseit required that the outer rotor drive shaft be of an objectionablylarge diameter. This, in turn, required the inner rotor drive shaft tobe even larger in diameter and both of these enlarged diameter driveshafts required transmission design compromise to accommodate connectionto such large drive shafts with the attendant mechanical complicationand added weight.

SUMMARY OF THE INVENTION A primary object of the present invention is toprovide a pitch control mechanism for the blades of a helicopter whichis capable of varying blade pitch cyclically about any selected axis andwhich is also capable of varying the blade pitch collectively and whichproduces a rotor head of minimum frontal area and drag.

In accordance with the present invention, the blade pitch controlmechanism is located internally of the rotor drive mechanism.

In accordance with a further aspect of the present invention, the pitchcontrol system taught herein can be used with either a single rotor orconcentric double rotors and with the pitch control swashplatepositioned in the rotor hub and with the swashplate control mechanismspassing through the rotor drive shaft, which is of minimum diametersince the swashplate is not positioned therein but in the rotor hub andis connected directly to pitch change horns projecting from the innerend of the blades into the hub, thereby no externally positioned pitchcontrol mechanisms to create drag.

In accordance with a further aspect of the present invention, twoZ-crank systems, which include two concentrically mounted torque tubesas the central legs of each Z, are connected at different stations tothe nonrotating portion of a swashplate so that translation of thetorque tubes will effect collective pitch change of the blades and sothat selective rotation of the torque tubes will produce universalcyclic pitch variation of the rotor blades about any selected axis.

In accordance with a further aspect of the invention, the first Z-crankarrangement permits cyclic pitch variation about an axis which is to theaxis about which the second Z- crank arrangement permits cyclic pitchvariation so that coaction of the two Z-crank mechanisms produces 3superimposed cyclic pitch variations to permit cyclic pitch controlabout any selected axis and to also produce collective pitch control,and wherein these axes may be parallel to the aircraft longitudinal andlateral axes.

This invention can be used either to so control the pitch of asingle-rotor or to control the pitch of multirotor aircraft and theparticular pitch control system can be used to control one or bothrotors or can be used in combination with another pitch control systemto control one of the rotors only while the other pitch control systemcontrols the pitch of the other l'OtOI'.

In accordancewith another feature of this invention, the pitch of theconcentric rotors can be controlled independently of one another.

In accordance with still a further feature of this invention, thecontrol levers of the two Z-crank mechanisms can be displaced axiallyfrom and on opposite sides of the swashplate assembly and the inputstherefrom to the swashplate assembly can be made by linkages reaching upor down from the control lever as the case may require, therebyproducing a minimum diameter rotor.

Another feature of the present invention is that by proper selection ofthe angle between the bearing axis and the torque tube axis of a givenZ-crank system, the amount of torque tube rotation required to effect agiven amount of tilt of the control lever axis and swashplate and hencecyclic pitch variation can be readily controlled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a showing of a portion of amodem aircraft, such as a helicopter, with a coaxial, counterrotatingrotor mechanism projecting therefrom and shown to be partially brokenaway to reveal the invention in this environment.

FIG. 2 is a schematic showing of a single Z-crank mechanism to beutilized to demonstrate the operation of such a mechanism.

FIG. 3 is a top view of the double Z-crank mechanism of this inventionsupporting the swashplate of a rotor pitch control system.

FIG. 4 is a perspective exploded showing of a double Z- crank mechanism.

FIG. 5 is a partial side view of the FIG. 4 construction showing theouter or upper Z-crank connection to the swashplate.

FIG. 6 is a partial side view of the FIG. 4 construction showing theinner or lower Z-crank connection to the swashplate.

FIG. 7 is a perspective showing of this pitch control system in acoaxial, counterrotating rotor system.

FIG. 8 is a crosssectional showing of a coaxial countenotating rotorsystem utilizing the invention and broken away to illustrate theinvention in this environment and its drive mechanism.

FIG. 9 is a side view of a modification of the pitch control system usedon a single rotor and utilizing a different helicopter environment.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 we seemodern aircraft 10 of the helicopter type which includes fuselage l2 andwhich has longitudinal axis 14 with lateral axis 16 projectingperpendicular thereto into and out of the plane of the drawing. Rotorassembly 20 is supported from within fuselage l2 and projects outwardlytherefrom to be rotatable about axis of rotation 22. Rotor assembly 20is illustrated as a concentric, counterrotating unit including outerrotor assembly 24, including hub 26 mounted for rotation about axis 22and including a plurality of blades 28 projecting therefrom for rotationtherewith and supported therefrom for pitch change motion aboutfeathering axis 30. Rotor assembly 20 also includes inner rotor assembly32, which is mounted for rotation about axis 22 and which includes rotorhub 34 and includes a plurality of blades 36 mounted therefrom forrotation therewith and for pitch change motion with respect theretoabout feathering axis 38. Rotor assembly 20 is supported from fuselage12 by transmission assembly 40 and rotors 24 and 32 are driven therebyin a fashion to be described in greater particularity hereinafter.

Aircraft l0 and rotors 24 and 32 may be of the type more particularlydisclosed and described in U.S. Pat. No. 3,409,249 with blades 28 and 36of the type more particularly described in U.S. Pat. No. 2,657,754.

The blades 36 of rotor assembly 32 are caused to change pitch inconventional fashion by swashplate mechanism 42, which is caused totranslate along and tilt with respect to axis 22 by a plurality ofselectively controlled servomechanisms 44. Swashplate 42 is connected topitch horn 46 of each blade 36 by pitch control rod 48 that is operatedin conventional fashion so that translation of swashplate 42 causescollective pitch change variation and tilt action of swashplate 42causes cyclic pitch variation of the blades of rotor 32. This pitchchange mechanism for rotor 32 is described in greater particularity inU.S. Pat. No. 3,199,601.

The invention herein relates to the way that the pitch of blades 28 ofrotor 24 is controlled and the rotor assembly 20 of FIG. 1 is partiallybroken away to permit a general showing of this construction. Blades 28of rotor 24 are controlled in pitch by swashplate 50 which is connectedto pitch control change horns 52 at the inner ends of blades 28 by pitchcontrol rod 54 so that translation of swashplate 50 along axis 22 willcause collective pitch variation of the blades 28 of rotor 24 andtilting action of swashplate 50 with respect to axis 22 will causecyclic pitch variation of blades 28. The position and motion ofswashplate 50 is controlled by first Z-crank mechanism 56 and secondZ-crank mechanism 58, which will both be described in greaterparticularity hereinafter, and which are supported from concentrictorque tubes 60 and 62. Torque tubes 60 and 62 are caused to translatealong axis 22 by servo piston-cylinder mechanism 64, which connectsthrough swivel link 66 to bearing 68, which is in turn connected to thetorque tubes through link members 70 and 72. This translatory motion ofthe torque tubes imparts a similar motion to swashplate 50 and acollective pitch change to blades 28. The torque tubes 60 and 62 can becaused to rotate with respect to axis 22, in unison or separately bycylinder piston servomechanisms 74 and 76, which are connected to tubes60 and 62, respectively, through crank elements 70 and 72 to cause therotary motion thereof and thereby establish tilt motion in swashplate 50to control the cyclic pitch of blades 28 of rotor 24.

For a full appreciation of the operation of pitch control mechanism ofblades 28, which includes two Z-crank mechanisms 56 and 58, it is deemeddesirable to first consider the operation of a single Z-crank mechanismand reference will now be made to FIG. 2. In this connection, where everpossible for purposes of continuity, the same reference numerals will beused in describing the FIG. 2 construction as were used in describing inthe FIG. I embodiment. For purposes of clarity, an angle of about 45 isillustrated in FIG. 2 between the bearing axis 84 and the torque tubeaxis 22, but it should be borne in mind that in practice this angle isactually much smaller and in the vicinity of about 10. 4

The first Z-crank mechanism 56 includes torque tube 60 which ispositioned concentrically about torque tube axis 22. Torque tube 60constitutes the central leg of the Z-crank mechanism and connects to oneof the end legs thereof; namely, tube or cylindrical portion 82 which isconcentric about bearing axis 84, which intersects axis 22 at point ofintersection 86 and which fonns an angle therewith as do the legs of Z.Ring bearing 88 is sleeved onto the outer diameter of member 82 andengages the inner cylindrical aperture 90 of control lever 92 so thatcontrol lever 92 is supported from torque tube 60 and member 82 so as topermit relative rotation between member 82 and control lever 92. Endpins 98 and 100 project from opposite ends of control lever 92 and areconcentric about control lever axis 102, which passes through point ofintersection 86.

Stationary scissors 94 connect control lever 92 to fixed standpipe 96 toprevent rotation of the control lever but to permit tilting thereof andrelative rotation of cylindrical member 82 therewithin so that, astorque tube 60 is caused to rotate about axis 22 by crank 70, member 82will be caused to rotate within control lever 92. Since control lever 92is restrained from rotating therewith by stationary scissors 94, controllever 92 is thereby caused to tilt or pivot about tilt axis 104, whichintersects point of intersection 86 and is perpendicular to the plane ofthe paper shown in FIG. 2 and to axes 102, 22, and 84. In practice, awobble ring, which is actually the nonrotating ring 106 of swashplate 50is supported by control lever 92 since end pins 98 and 100 are receivedin apertures 108 and 110 thereof. And accordingly, ring 106, ifrestrained from rotation about axis 102, will tilt with control lever 92about tilt axis 104.

Actually, in our pitch control mechanism 80, a second 2- crank mechanism58 is used with mechanism 56 shown schematically in FIG. 2 and includescomparable mechanism to cause swashplate nonrotatable ring 106 to alsobe pivotable or tiltable about axis 102, which is perpendicular to axis104. Axes 102 and 104 are orthogonal.

A top view of such a double Z-crank arrangement is shown in FIG. 3. Thesame reference numerals used to identify the parts of first Z-crankmechanism 56 in FIG. 2 are also used in FIG. 3 and the mechanism of thesecond Z-crank mechanism 58 will now be described. Tube member 120 is ofcircular cross section and concentric about a second bearing axis 121passing through point of intersection 86 and constitutes a first leg ofthe Z of the second Z-crank mechanism 58, which forms an angle with andprojects from torque tube 62 in the same fashion that correspondingcylindrical mechanism 82 projects from torque tube 60 in FIG. 2. Ringbearing 122 is sleeved onto member 120 and. received in the cylindricalinner aperture 124 of the second control lever 126 so that control lever126 is supported from central member 120 and relative rotationtherebetween is permitted. End pins 128 and 130 project from theopposite ends of control lever 126 and are concentric about axis 104which is the control lever axis for Z- crank mechanism 58 and, also, thetilt axis for Z-crank mechanism 56. End pins 128 and 130 pass throughapertures 132 and 134 in nonrotating swashplate ring 106, whichapertures are in diametrical alignment with one another and positioned90 from the diametrically aligned apertures 108 and 110, which receiveend pins 98 and 100 of the first Z- crank mechanism 56. Stationaryscissors 94 are shown connected to ring 106 in FIG. 3 but it is obviousthat it could as well be connected to control levers 92 or 126 since itperforms the function of preventing these three elements from rotatingabout axis 22.

With the mechanism of FIG. 3 just described it will be evident that withswashplate ring 106 restrained from rotation, the rotation of torquetube 60 will cause swashplate 50 to tilt about axis 104 and rotation oftorque tube 62 will cause swashplate 50 to tilt about axis 102. Thistilting action will be imparted to swashplate rotary member 140 andtherefrom by connecting rods such as 54 (FIG. 1) to a pitch change horn52 at the inner ends of each blade 28 to cause pitch variation thereof.

We have illustrated a construction in FIG. 3 in which the swashplate 50is tiltable about perpendicular axes 102 and 104. While a concentricrotor configuration is shown with concentric torque tubes 60 and 62, inpractice torque tubes 60 and 62 need not be concentric and need not bein alignment so long as the bearing axes, such as 84, the axes ofrotation, such as 22, and the control lever axes, such as 102, ofZ-crank mechanism 56 and 58 intersect in a common point, such as pointof intersection 86.

Now referring to FIGS. 4 through 6, we see anexploded view and sectionsthereof of a double Z-crank mechanism system 80 imparting cyclic pitchvariations to the stationary member 106 of the rotor swashplate whereinthe lower 2- crank mechanism 56 is shown producing at 0 cyclic pitchinput and the upper or outer Z-crank mechanism 58 is shown imparting acyclic input of angle a. FIG. 4 shows that torque tube 60 of Z-crankmechanism 56, torque tube supporting standpipe 96, ring 106, and torquetube 62 of Z crank mechanism 58 are positioned concentrically aboutrotor axis of rotation and torque tube axis of rotation 22. Stationaryscissors 94 project between fixed standpipe 96 and swashplatenonrotating ring 106 to prevent rotation of ring 106 about axis 22,while permitting tilting action thereof in a conventional fashion.Viewing the bottom portion of FIG. 4 and FIG. 6 it will be seen thatZ-crank mechanism 56 includes torque tube 60 which is concentric aboutaxis 22 and which includes a first end 82 which is of circular crosssection and concentric about bearing axis 84 which forms an angle withaxis 82 and defines point of intersection 86 therewith. Ring bearing 88is received onto the outer surface of sleeve 82 and in turn receivescontrol lever 92 outwardly thereof to permit relative rotation betweenmembers 82 and 92. Control lever 92, as will be shown in greaterparticularity hereinafter, will be positioned below ring 106 andtherefore projects in any convenient fashion upwardly from bearingsupport tube 82 so as to support end pins 98 and 100 in spaced relationtherefrom and concentrically about control lever axis 102. Since pins 98and 100 are received in apertures 108 and 110 of swashplate nonrotatingring 106, it will be seen that Z-crank mechanism 56 performs thefunction of supporting ring 106 for tilt motion about axis 102, whichmay be parallel to the aircraft longitudinal axis and perpendicular tothe aircraft lateral axis or vice versa. Further viewing of these FIGS.shows that in Z-crank mechanism 56 axes 84, 22, and 102 intersect atpoint of intersection 86.

Now viewing the upper portion of FIG. 4 and FIG. 5, we see Z-crankmechanism 58 consisting of torque tube 62 positioned concentricallyabout axis 22 and having bearing support sleeve projecting therefrom atangle a so that bearing support tube 120 is concentric about bearingaxis 121. Ring bearing 122 supports control lever 126 from sleeve 120and concentrically about axis 121 and, since Z-crank mechanism 58 isgoing to be positioned above ring 106, as shown in greater particularityhereinafter, control lever 126 is shaped in any convenient fashion toproject downwardly so as to support end pins 128 and 130 concentricallyabout control lever axis 105, which in view of the cyclic control inputillustrated in these FIGS. to the Z-crank mechanism 58, is angularlyoffset with respect to axis 104 by angle a and is orthogonal with axis102. It will be noted that in Z-crank mechanism 58, as in the previouslydescribed mechanism 56, bearing axis 121, control lever axis 105 andaxis of rotation 22 intersect at point of intersection 86 which, is thecommon point of intersection for the comparable axes of Z-crankmechanism 56 and this axis intersection is necessary to permit theoffset relationship between swashplate ring 106 and the bearings andbearing support ends of Z-crank members 56 and 58 on opposite sidesthereof to permit the fabrication of a minimum-diameter rotor assembly80.

FIGS. 46 show that the coaction of Z-crank mechanisms 56 and 58 is tosupport swashplate nonrotating ring 106 to be tiltable about axis 102,since there is zero cyclic input to Z- crank mechanism 56, and aboutaxis 105, which is angularly offset from axis 104 by the amount ofcyclic pitch input being imparted to the rotor by Z-crank mechanism 58,namely angle a. Axes 102 and 104 are the axes of zero cyclic pitch inputand are preferably positioned 90 apart for optimum results since anydeviation therefrom would cause undesirable feedback from one of theZ-crank mechanisms to the other.

Now referring to FIG. 7 we see the double Z-crank pitch control system80 which has just been described in connection with FIGS. 46 in itsassembled condition. It will be noted therefrom that fixed standpipe 96,and torque tubes 60 and 62 are positioned concentrically about axis ofrotation 22 and that Z-crank mechanisms 56 and 58 are positioned on theopposite side of ring 106 along axis 22, thereby permitting the pitchcontrol mechanism 80 of FIG. 7 to be of a lesser diameter than wouldhave to be the case if Z-crank mechanisms 56 and 58 were insubstantially radial alignment with ring 106 and its associatedswashplate parts. The plane of axes 102 and 104 is the plane ofswashplate nonrotating ring 106 when there is zero cyclic pitch input tothe rotor blades and it is important to note that the axis of rotation22, the bearing axes 84 and 121, and the control lever axes 102 and 105of Z-crank mechanisms 56 and 58, respectively, together with axis 104,all pass through common point of intersection 86. By viewing FIG. 7 itwill be evident that by rotating torque tube 62 about axis 22, Z-crankmechanism 58 will cause swashplate ring 106 to tilt about axis 102,which is the zero cyclic pitch input axis for this Z-crank mechanism,and that rotation of torque tube 60 of Z-crank mechanism 56 will causeswashplate ring 106 to tilt about axis 105, which is offset from thezero cyclic pitch input axis 104 by the amount of cyclic pitch impartedto ring 106, namely angle a. It will also be evident that bysimultaneous and selective rotation of torque tubes 60 and 62, ring 106,due to the superimposed action thereon of Z-cranks 56 and 58 can bebrought to tilt about any arbitrary axis so that mechanism 80 isuniversal in nature in this respect and can produce any desired cyclicpitch.

Now referring to FIG. 8 we see a side cross-sectional view of rotorassembly shown in greater particularity than in FIG. 1. It will be notedthat torque tube 62 of Z-crank assembly 58 is positioned concentricallyabout axis 22 and within torque tube 60 of Z-crank assembly 56, which isin turn positioned within cylindrical standpipe 96. Standpipe 96 issupported within cylindrical support 150, which is received in matingrelation at the base thereof in fixed transmission housing 152. Rotordrive shaft 154 for outer or upper rotor 24 is of circular cross sectionand concentric about axis 22 and supported from central cylindricalsupport 150 by bearing assembly 156. Lower or inner rotor drive shaft160 is supported from upper rotor drive shaft 154 by bearing units 162and 164, and from transmission housing 152 by bearing 166.

Rotor assembly 20 is driven by engine 170, which may be of anyconventional type such as that taught in U.S. Pat. Nos. 2,71 1,631 and2,747,367, through transmission 40. Appropriate drive mechanism of aconventional nature 172 connects engine 170 in driving relation to aconventional transmission 174 of the type shown in U.S. Pat. No.2,522,443 to drive shafts or torque tubes 60 and 62 in oppositedirections.

The upper end of torque tube 62 is supported by cylindrical supportmember 210 which projects into and is splined to inner cylindricalsurface 51 of first end 82 of torque tube 62 such that it is rotatablewith and axially displaceable with respect to torque tube 62 about axis22. Support member 210 is supported from hub 26 by flange member 212through bearing 53 which permits relative rotation between flange 212and support member 210.

While the construction shown so far has the advantage that the entirepitch control mechanism 80 for outer rotor 24 can be carried inwardly ofthe drive shaft mechanisms 1160 and 154 and thereby permit the use of aconstruction which is of a lesser diameter about axis 22, than would bethe case if conventional pitch control means such as the hydrauliccylinders 48 of rotor 32 were used therewith, other constructions arepossible. For example, in the construction shown in FIG. 9, the controlmechanism 80' for a single-rotor helicopter is positioned outwardly ofthe helicopter rotor 24 which is, in turn, positioned immediatelyadjacent transmission 40 of the type described in connection with FIG.8. In this construction, swashplate 50, and the ends of Z-crankmechanisms 56 and 58 which connect thereto are substantially in radialalignment and therefore a construction of minimum height projecting fromfuselage I2 is achieved. Such a construction permits the use of shortdrive shafts between the transmission 40 and the rotor 24 but does notpermit the pitch control mechanism rods 48, which extend betweenswashplate 50 and blades 28, to be positioned within the rotor hub 26.Pitch control mechanism is otherwise similar to that shown and describedin connection with FIG. 8 and the same reference numerals have beenimparted thereto for identification purposes.

lclaim:

1. A pitch control system for a helicopter rotor having a plurality ofblades mounted for rotation and blade pitch variation including:

a. a first torque tube mounted for rotation about an axis of rotationand having a first end of circular cross section positionedconcentrically about a first bearing axis which forms an angle with andintersects said axis of rotation is to define a point of intersectiontherewith;

b. a first bearing member enveloping said first end of said first torquetube and positioned concentrically about said first bearing axis;

c. a first control lever including a circular central portionconcentrically enveloping said bearing member to be supported therefromby said first end of said first torque tube and so as to permit rotationtherebetween and including end pins projecting from opposite sidesthereof concentrically about a first control lever axis passing throughsaid point of intersection;

d. a swashplate nonrotating ring positioned along said axis of rotationin spaced relation in a first direction from said first bearing memberand said first control lever and including two sets of diametricallyopposed apertures spaced perpendicular to one another and with said endpins received in the first of said aperture sets so that said swashplatenonrotatable ring is supported by said control lever end pins;

e. a second torque tube concentric about said axis of rotation with saidfirst torque tube and including a first end of circular cross sectionpositioned concentrically about a second bearing axis which forms anangle with said axis of rotation and passes through said point ofintersection;

f. a second bearing member enveloping said first end of said secondtorque tube and positioned along said axis of rotation in spacedrelation in said first direction from said swashplate nonrotating ringand concentrically about said second bearing axis;

g. a second control lever positioned along said axis of rotation inspaced relation in said first direction from said swashplate nonrotatingring and having a circular central opening enveloping said secondbearing member so'that said second control lever is supported throughsaid second bearing unit by said second torque tube first end andincluding end pins projecting from the opposite ends thereofconcentrically about a second control lever axis which is perpendicularto said first control lever axis and with said end pins received in thesecond set of apertures of said nonrotatable swashplate member;

h. means to prevent said nonrotatable swashplate member from rotating sothat rotation of said first torque tube will cause said nonrotatableswashplate member to tilt about a first tilt axis and thereby vary bladepitch cyclically about said first tilt axis and so that rotation of saidsecond torque tube will cause said nonrotatable swashplate member totilt about a second tilt axis which is perpendicular to said first tiltaxis and thereby vary blade pitch cyclically about said second tiltaxis;

i. a rotatable swashplate member supported by and rotatable with respectto said nonrotatable swashplate member; and

j. means connecting said rotatable swashplate member to the blades ofthe rotor for pitch change motion therewith.

2. Apparatus according to claim 1 wherein said rotor has an axis ofrotation and wherein said torque tube axis of rotation is coincidentwith the rotor axis of rotation.

3. Apparatus according to claim 1 and including means to support saidtorque tubes for translation along and rotation about said axis ofrotation.

4. Apparatus according to claim 3 and including means to cause saidtorque tubes to translate in unison along said axis of rotation andhence to cause said swashplate to so translate to thereby vary the pitchof said blades collectively.

5. Apparatus according to claim 3 and including means to selectivelyrotate said torque tubes about said axis of rotation individually or inunison to vary the position of said swashplate selectively about each ofsaid tilt axes.

6. Apparatus according to claim 4 and including means to selectivelyrotate said torque tubes about said axis of rotation individually or inunison to vary the position of said swashplate selectively about each ofsaid tilt axes.

7. A helicopter having a longitudinal and a transverse axis and:

a. a first rotor including a hub mounted for rotation about an axis ofrotation and a plurality of blades extending therefrom for rotationtherewith and mounted for pitch change motion with respect thereto;

b. a second rotor including a hub mounted for rotation about said axisof rotation and including a plurality of blades mounted for rotationtherewith and for pitch change motion with respect thereto;

a rotor drive shaft concentric about said axis of rotation and extendingthrough the hub of said second rotor and connected to the hub of saidfirst rotor;

. means to cause said rotor drive shaft to rotate about said axis ofrotation;

. means to cause said second rotor to rotate about said axis ofrotation; means to cause the blades of said second rotor to vary inpitch with respect to the hub thereof;

. means to cause the blades of said first rotor to vary in pitch withrespect to the hub thereof and including:

1. a first torque tube positioned within said rotor drive shaft andmounted for translation along and rotation about said axis of rotationand having a first end of circular cross section positionedconcentrically about a first bearing axis which forms an angle with andintersects said axis of rotation to define a point of intersectiontherewith;

2. a first bearing member enveloping said first end of said first torquetube and positioned concentrically about said first bearing axis;

. a first control lever including a circular central portionconcentrically enveloping said bearing member to be supported therefromby said first end of said first torque tube and so as to pennit rotationtherebetween and including end pins projecting from opposite sidesthereof concentrically about a first control lever axis passing throughsaid point of intersection;

4. a swashplate nonrotating ring positioned along said axis of rotationin spaced relation in a first direction from said first bearing memberand said first control lever and including two sets of diametricallyopposed apertures spaced perpendicular to one another and with said endpins received in the first of said aperture sets so that said swashplatenonrotatable ring is supported by said control lever end pins;

5. a second torque tube positioned within said rotor shaft and saidfirst torque tube and concentric about said axis of rotation with saidfirst torque tube and mounted for translation along and rotation aboutsaid axis of rotation and including a first end of circular crosssection positioned concentrically about a second bearing axis whichforms an angle with said axis of rotation and passes through said pointof intersection;

6. a second bearing member enveloping said first end of said secondtorque tube and positioned along said axis of rotation in spacedrelation in said first direction from said swashplate nonrotating ringand concentrically about said second bearing axis;

7. a second control lever positioned along said axis of rotation inspaced relation in said first direction from said swashplate nonrotatingring and having a circular central opening enveloping said secondbearing member so that said second control lever is supported throughsaid second bearing unit by said second torque tube first end andincluding end pins projecting from the opposite ends thereofconcentrically about a second control lever axis which is perpendicularto said first control lever axis and with said end pins received in thesecond set of apertures of said nonrotatable swashplate member;

8. means to prevent said nonrotatable swashplate member from rotating sothat rotation of said first torque tube will cause said nonrotatableswashplate member to tilt about a first tilt axis which passes throughsaid point of intersection and which is perpendicular'to said axis ofrotation when at zero pitch setting, said first bearing axis and saidfirst control lever axis and thereby vary blade pitch cyclically aboutsaid first tilt axis and so that rotation of said second torque tubewill cause said nonrotatable swashplate member to tilt about a secondtilt axis which is perpendicular to said first tilt axis and iscoincident with said first control lever axis and thereby vary bladepitch cyclically about said second tilt axis;

9. a rotatable swashplate member supported by and rotatable with respectto said nonrotatable swashplate member; and

10. means connecting said rotatable swashplate member to the blades ofthe rotor for pitch change motion therewith.

8. Apparatus according to claim 7 and wherein said second rotor bladeshave pitch change horns projecting therefrom and including means tochange the pitch of the blades of said second rotor including:

a. a swashplate mounted for translation and tilting with respect to saidaxis of rotation;

b. means connecting said swashplate to said pitch change horns; and

c. servo means in the form of hydraulic cylinder piston units connectedto said swashplate to cause said swashplate to translate along and tiltwith respect to said axis of rotation.

9. Blade pitch control mechanism for a multibladed rotor of thehelicopter type including:

a. a first Z-crank mechanism having a tubular center leg mounted fortranslation along and rotation about an axis of rotation and furtherhaving a first end of circular cross section concentric about a firstbearing axis forming an angle with said axis of rotation andintersecting the axis of rotation to form a point of intersection;

b. a first control lever having a circular aperture in the interiorthereof and mounted around said first end of said first Z-crankmechanism to permit relative rotation between said first control leverand said first Z-crank mechanism first end and having end pinsprojecting from the opposite ends thereof and positioned concentricallyabout first control lever axis passing through said point ofintersection;

. a second Z-crank mechanism including a tubular central leg mountedconcentrically with said tubular central leg of said first Z-crankmechanism for translation along and rotation about said axis of rotationand having a first end of circular cross section positionedconcentrically about a second bearing axis forming an angle with saidaxis of rotation and passing through said point of intersection;

d. a second control lever having a circular aperture in the interiorthereof and mounted about said first end of said second Z-crankmechanism to permit relative rotation therebetween and including endpins projecting from the opposite ends thereof and positionedconcentrically about a second control lever axis passing through saidpoint intersection;

e. a swashplate assembly positioned along said axis of rotation betweensaid first and second control lever and including:

1. a nonrotatable ring member having two sets of diametrically opposedapertures therein spaced 90 apart and supported by said control leverswith said end pins of said first control lever being received in saidfirst set of apertures and said end pins of said second control leverbeing received in said second set of mechanism will cause saidnonrotatable swashplate member to tilt about a second tilt axis which isperpendicular to said first tilt axis and thereby vary blade pitchcyclically about said second tilt axis; and

g. means connecting said rotatable swashplate member to each of theblades to cause the blades to change pitch in accordance with swashplatemotion.

10. Apparatus according to claim 9 and including:

a. means to cause said Z-crank mechanism to translate in unison alongsaid axis of rotation; and

b. means to cause said Z-crank mechanisms to rotate about said axis ofrotation.

11. Apparatus according to claim 10 wherein said Z-crank mechanismsrotating means includes means to rotate said first Z-crank mechanism andmeans independent thereof to rotate said second Z-crank mechanism tothereby accomplish universal blade cyclic pitch variation.

1. A pitch control system for a helicopter rotor having a plurality ofblades mounted for rotation and blade pitch variation including: a. afirst torque tube mounted for rotation about an axis of rotation andhaving a first end of circular cross section positioned concentricallyabout a first bearing axis which forms an angle with and intersects saidaxis of rotation is to define a point of intersection therewith; b. afirst bearing member enveloping said first end of said first torque tubeand positioned concentrically about said first bearing axis; c. a firstcontrol lever including a circular central portion concentricallyenveloping said bearing member to be supported therefrom by said firstend of said first torque tube and so as to permit rotation therebetweenand including end pins projecting from opposite sides thereofconcentrically about a first control lever axis passing through saidpoint of intersection; d. a swashplate nonrotating ring positioned alongsaid axis of rotation in spaced relation in a first direction from saidfirst bearing member and said first control lever and including two setsof diametrically opposed apertures spaced perpendicular to one anotherand with said end pins received in the first of said aperture sets sothat said swashplate nonrotatable ring is supported by said controllever end pins; e. a second torque tube concentric about said axis ofrotation with said first torque tube and including a first end ofcircular cross section positioned concentrically about a second bearingaxis which forms an angle with said axis of rotation and passes throughsaid point of intersection; f. a second bearing member enveloping saidfirst end of said second torque tube and positioned along said axis ofrotation in spaced relation in said first direction from said swashplatenonrotating ring and concentrically about said second bearing axis; g. asecond conTrol lever positioned along said axis of rotation in spacedrelation in said first direction from said swashplate nonrotating ringand having a circular central opening enveloping said second bearingmember so that said second control lever is supported through saidsecond bearing unit by said second torque tube first end and includingend pins projecting from the opposite ends thereof concentrically abouta second control lever axis which is perpendicular to said first controllever axis and with said end pins received in the second set ofapertures of said nonrotatable swashplate member; h. means to preventsaid nonrotatable swashplate member from rotating so that rotation ofsaid first torque tube will cause said nonrotatable swashplate member totilt about a first tilt axis and thereby vary blade pitch cyclicallyabout said first tilt axis and so that rotation of said second torquetube will cause said nonrotatable swashplate member to tilt about asecond tilt axis which is perpendicular to said first tilt axis andthereby vary blade pitch cyclically about said second tilt axis; i. arotatable swashplate member supported by and rotatable with respect tosaid nonrotatable swashplate member; and j. means connecting saidrotatable swashplate member to the blades of the rotor for pitch changemotion therewith.
 2. Apparatus according to claim 1 wherein said rotorhas an axis of rotation and wherein said torque tube axis of rotation iscoincident with the rotor axis of rotation.
 2. a rotatable ring membermounted for rotation and supported from said nonrotatable ring member;f. means to prevent rotation of said nonrotatable ring member so thatrotation of said tubular leg of said first Z-crank mechanism will causesaid nonrotatable swashplate member to tilt about a first tilt axis andthereby vary blade pitch cyclically about said first tilt axis and sothat rotation of said tubular leg of said second Z-crank mechanism willcause said nonrotatable swashplate member to tilt about a second tiltaxis which is perpendicular to said first tilt axis and thereby varyblade pitch cyclically about said second tilt axis; and g. meansconnecting said rotatable swashplate member to each of the blades tocause the blades to change pitch in accordance with swashplate motion.2. a first bearing member enveloping said first end of said first torquetube and positioned concentrically about said first bearing axis;
 3. afirst control lever including a circular central portion concentricallyenveloping said bearing member to be supported therefrom by said firstend of said first torque tube and so as to permit rotation therebetweenand including end pins projecting from opposite sides thereofconcentrically about a first control lever axis passing through saidpoint of intersection;
 3. Apparatus according to claim 1 and includingmeans to support said torque tubes for translation along and rotationabout said axis of rotation.
 4. a swashplate nonrotating ring positionedalong said axis of rotation in spaced relation in a first direction fromsaid first bearing member and said first control lever and including twosets of diametrically opposed apertures spaced perpendicular to oneanother and with said end pins received in the first of said aperturesets so that said swashplate nonrotatable ring is supported by saidcontrol lever end pins;
 4. Apparatus according to claim 3 and includingmeans to cause said torque tubes to translate in unison along said axisof rotation and hence to cause said swashplate to so translate tothereby vary the pitch of said blades collectively.
 5. Apparatusaccording to claim 3 and including means to selectively rotate saidtorque tubes about said axis of rotation individually or in unison tovary the position of said swashplate selectively about each of said tiltaxes.
 5. a second torque tube positioned within said rotor shaft andsaid first torque tube and concentric about said axis of rotation withsaid first torque tube and mounted for translation along and rotationabout said axis of rotation and including a first end of circular crosssection positioned concentrically about a second bearing axis whichforms an angle with said axis of rotation and passes through said pointof intersection;
 6. a second bearing member enveloping said first end ofsaid second torque tube and positioned along said axis of rotation inspaced relation in said first direction from said swashplate nonrotatingring and concentrically about said second bearing axis;
 6. Apparatusaccording to claim 4 and including means to selectively rotate saidtorque tubes about said axis of rotation individually or in unison tovary the position of said swashplate selectively about each of said tiltaxes.
 7. a second control lever positioned along said axis of rotationin spaced relation in said first direction from said swashplatenonrotating ring and having a circular central opening enveloping saidsecond bearing member so that said second control lever is supportedthrough said second bearing unit by said second torque tube first endand including end pins projecting from the opposite ends thereofconcentrically about a second control lever axis which is perpendicularto said first control lever axis and with said end pins received in thesecond set of apertures of said nonrotatable swashplate member;
 7. Ahelicopter having a longitudinal and a transverse axis and: a. a firstrotor including a hub mounted for rotation about an axis of rotation anda plurality of blades extending therefrom for rotation therewith andmounted for pitch change motion with respect thereto; b. a second rotorincluding a hub mounted for rotation about said axis of rotation andincluding a plurality of blades mounted for rotation therewith and forpitch change motion with respect thereto; c. a rotor drive shaftconcentric about said axis of rotation and extending through the hub ofsaid second rotor and connected to the hub of said first rotor; d. meansto cause said rotor drive shaft to rotate about said axis of rotation;e. means to cause said second rotor to rotate about said axis ofrotation; f. means to cause the blades of said second rotor to vary inpitch with respect to the hub thereof; g. means to cause the blades ofsaid first rotor to vary in pitch with respect to the hub thereof andincluding:
 8. means to prevent said nonrotatable swashplate member fromrotating so that rotation of said first torque tube will cause saidnonrotatable swashplate member to tilt about a first tilt axis whichpasses through said point of intersection and which is perpendicular tosaid axis of rotation when at zero pitch setting, said first bearingaxis and said first control lever axis and thereby vary blade pitchcyclically about said first tilt axis and so that rotation of saidsecond torque tube will cause said nonrotatable swashplate member totilt about a second tilt axis which is perpendicular to said first tiltaxis and is coincident with said first control lever axis and therebyvary blade pitch cyclically about said second tilt axis;
 8. Apparatusaccording to claim 7 and wherein said second rotor blades have pitchchange horns projecting therefrom and including means to change thepitch of the blades of said second rotor including: a. a swashplatemounted for translation and tilting with respect to said axis ofrotation; b. means connecting said swashplate to said pitch changehorns; and c. servo means in the form of hydraulic cylinder piston unitsconnected to said swashplate to cause said swashplate to translate alongand tilt with respect to said axis of rotation.
 9. a rotatableswashplate member supported by and rotatable with respect to saidnonrotatable swashplate member; and
 9. Blade pitch control mechanism fora multibladed rotor of the helicopter type including: a. a first Z-crankmechanism having a tubular center leg mounted for translation along androtation about an axis of rotation and further having a first end ofcircular cross section concentric about a first bearing axis forming anangle with said axis of rotation and intersecting the axis of rotationto form a point of intersection; b. a First control lever having acircular aperture in the interior thereof and mounted around said firstend of said first Z-crank mechanism to permit relative rotation betweensaid first control lever and said first Z-crank mechanism first end andhaving end pins projecting from the opposite ends thereof and positionedconcentrically about first control lever axis passing through said pointof intersection; c. a second Z-crank mechanism including a tubularcentral leg mounted concentrically with said tubular central leg of saidfirst Z-crank mechanism for translation along and rotation about saidaxis of rotation and having a first end of circular cross sectionpositioned concentrically about a second bearing axis forming an anglewith said axis of rotation and passing through said point ofintersection; d. a second control lever having a circular aperture inthe interior thereof and mounted about said first end of said secondZ-crank mechanism to permit relative rotation therebetween and includingend pins projecting from the opposite ends thereof and positionedconcentrically about a second control lever axis passing through saidpoint intersection; e. a swashplate assembly positioned along said axisof rotation between said first and second control lever and including:10. Apparatus according to claim 9 and including: a. means to cause saidZ-crank mechanism to translate in unison along said axis of rotation;and b. means to cause said Z-crank mechanisms to rotate about said axisof rotation.
 10. means connecting said rotatable swashplate member tothe blades of the rotor for pitch change motion therewith.
 11. Apparatusaccording to claim 10 wherein said Z-crank mechanisms rotating meansincludes means to rotate said first Z-crank mechanism and meansindependent thereof to rotate said second Z-crank mechanism to therebyaccomplish universal blade cyclic pitch variation.